Ch. 3: Describing Sound Waves

Question 1

Parameters describe features of a ____ ____

Answer 1

Parameters describe features of a sound wave

Question 2

The values of seven parameters are required to completely characterize a ____ ____

Answer 2

The values of seven parameters are required to completely characterize a sound wave

Question 3

The ____ of a sound wave is the ultrasound system and ____

Answer 3

The source of a sound wave is the ultrasound system and transducer

Question 4

Some parameters are determined by the ____ through which the ____ is traveling; The tissue is also called the ____

Answer 4

Some parameters are determined by the tissue through which the sound is traveling; The tissue is also called the medium

Question 5

Features of a sound wave:

Answer 5

• Definition
  
  • Units
  • Typical values
  • Determined/established by
  • Adjustable
  • Formula/concept

Question 6

• 1 Cycle:
  
  • 1 ____ and 1 ____
  • The start of a ____ to the start of the next ____

Answer 6

• 1 Cycle:
  
  • 1 Compression and 1 Rarefaction
  • The start of a cycle to the start of the next cycle

Question 7

Period

• Definition— Period is the ____ it takes a wave to ____ a single ____, or the time from the start of one ____ to the start of the next ____
• Units— Period is reported in units of ____, such as ____ (µs), seconds, hours, or days
• Typical values— The typical value of period in diagnostic ultrasound is ____ to ____ ____ (µs)
  
  • This may also be written as:
    
    • 6 x 10⁻⁸ to 5 x 10⁻⁷ seconds
    • 0.06 to 0.5 µs
    • 0.000 000 06 to 0.000 000 5 seconds
• Determined by— Period is determined by the ____ only, not by the ____
• Adjustable— ____. The sonographer ____ change the period while using a basic ultrasound system with a particular transducer
• Formula— ____

Answer 7

Period

• Definition— Period is the time it takes a wave to vibrate a single cycle, or the time from the start of one cycle to the start of the next cycle
• Units— Period is reported in units of time, such as microseconds (µs), seconds, hours, or days
• Typical values— The typical value of period in diagnostic ultrasound is 0.06 to 0.5 microseconds (µs)
  
  • This may also be written as:
    
    • 6 x 10⁻⁸ to 5 x 10⁻⁷ seconds
    • 0.06 to 0.5 µs
    • 0.000 000 06 to 0.000 000 5 seconds
• Determined by— Period is determined by the sound source only, not by the medium
• Adjustable— No. The sonographer cannot change the period while using a basic ultrasound system with a particular transducer
• Formula— P = 1/f

Question 8

Frequency

• Definition— Frequency is the ____ of particular events that occur in a specific duration of time
  
  • For example, the frequency of presidential elections in the United States is 25 times per century
    • The frequency of the menstrual cycle is 12 times per year
  • In diagnostic sonography, the frequency of a wave is described as the number of ____ that occurs in ____ ____
• Units— Frequency is reported in units ____ ____ , 1/second, ____ (Hz)
  
  • Hertz is another way to say “____ ____ ”
  • 1 cycle/second = 1 hertz
  • 1,000 cycles/second = ____ ____
  • 1,000,000 cycles/second = ____ ____
• Typical values— In clinical imaging, frequency ranges from approximately ____ ____ to ____ ____
  
  • Another way to say this is ____ ____ to ____ ____ per ____
• Determined by— Frequency of a sound wave is determined by the ____ only, not by the ____ through which the sound is traveling
• Adjustable— ____ . The sonographer ____ change the frequency while using a basic ultrasound system and transducer
• Formula— ____

Answer 8

Frequency

• Definition— Frequency is the number of particular events that occur in a specific duration of time
  
  • For example, the frequency of presidential elections in the United States is 25 times per century
    
    • The frequency of the menstrual cycle is 12 times per year
  • In diagnostic sonography, the frequency of a wave is described as the number of cycles that occurs in one second
• Units— Frequency is reported in units per second, 1/second, Hertz (Hz)
  
  • Hertz is another way to say “per second”
  • 1 cycle/second = 1 hertz
  • 1,000 cycles/second = 1 kHz
  • 1,000,000 cycles/second = 1 MHz
• Typical values— In clinical imaging, frequency ranges from approximately 2 MHz to 15 MHz
  
  • Another way to say this is 2 million to 15 million per seconds
• Determined by— Frequency of a sound wave is determined by the sound source only, not by the medium through which the sound is traveling
• Adjustable— No. The sonographer cannot change the frequency while using a basic ultrasound system and transducer
• Formula— F = 1/P

Question 9

Frequency of infrasound:

Answer 9

Less than 20 Hz/0.02 kHz

Question 10

Frequency of audible sound:

Answer 10

Between 20 Hz/0.02 kHz and 20,000 Hz/20 kHz

Question 11

Frequency of ultrasound:

Answer 11

Greater than 20,000 Hz/20 kHz

Question 12

How did ultrasound get its name?

• ____ is classified based on the ability of humans to hear it
• If the ____ of a sound wave is less than ____ Hz, it is below the threshold of human hearing and cannot be heard
• That is, the sound is ____
• Sound waves with frequencies this low are defined as infrasonic or ____
• Humans can hear sound with frequencies between ____ Hz and ____ Hz
• This is called ____
• Sound with frequencies so high that humans ____ hear it is called ultrasonic or ____
• Ultrasound’s frequency is higher than ____ Hz (____ kHz)

Answer 12

How did ultrasound get its name?

• Sound is classified based on the ability of humans to hear it
• If the frequency of a sound wave is less than 20 Hz, it is below the threshold of human hearing and cannot be heard
• That is, the sound is inaudible
• Sound waves with frequencies this low are defined as infrasonic or infrasound
• Humans can hear sound with frequencies between 20 Hz and 20,000 Hz
• This is called audible
• Sound with frequencies so high that humans cannot hear it is called ultrasonic or ultrasound
• Ultrasound’s frequency is higher than 20,000 Hz (20 kHz)

Question 13

Why is frequency important in diagnostic sonography?

• Frequency is important in sonography because it affects ____ and ____ ____
• [Penetration— ____ ____]
• [Image quality— ____ ____]
• As frequency increases, penetration is ____, and image quality/detail is ____
• As frequency decreases, penetration is ____ ____, and image quality/detail is ____

Answer 13

• Frequency is important in sonography because it affects penetration and image quality
• [Penetration— How deep]
• [Image quality— Image resolution]
• As frequency increases, penetration is deeper, and image quality/detail is higher
• As frequency decreases, penetration is more shallow, and image quality/detail is less

Question 14

What is the Relationship between Frequency and Period?

• Period and frequency are ____ ____ to each other
• As frequency ____, period decreases
• As frequency decreases, period ____
• If one of these parameters remains constant, then the other remains ____
• Period and frequency have an even more special relationship that is called ____
• When two reciprocal parameters are multiplied together, the result is ____
  
  • Period x Frequency = ____
  • (The ____ it takes a wave to ____ a single cycle) x (the ____ of cycles that occurs in ____ second) = 1
• Use complimentary units:
  
  • Seconds and ____
  • ____ and kilohertz

Answer 14

What is the Relationship between Frequency and Period?

• Period and frequency are inversely related to each other
• As frequency increases, period decreases
• As frequency decreases, period increases
• If one of these parameters remains constant, then the other remains unchanged
• Period and frequency have an even more special relationship that is called reciprocal
• When two reciprocal parameters are multiplied together, the result is 1
  
  • Period x Frequency = 1
  • (The time it takes a wave to vibrate a single cycle) x (the # of cycles that occurs in 1 second) = 1
• Use complimentary units:
  
  • Seconds and hertz
  • Milliseconds and kilohertz

Question 15

More about Hertz

• Frequency is reported with units of ____
• Some people believe that hertz means “____ ____ ____”
  
  • (1) Hertz means events per second
  • (2) To which event are we referring?
• For example, what is the meaning of a sound wave with a frequency of 100 Hz?
  
  • (1) 100 events occur each second
  • (2) A cycle is our event. In this case, 100 Hz means 100 ____ per second
• What is the meaning of a flat-screen TV with a frame rate of 120 Hz?
  
  • (1) 120 events occur each second
  • (2) A frame is our event. Thus, the TV displays 120 frames per second
• What is the meaning of an individual with a heart rate of 1 Hz?
  
  • (1) One event occurs each second
  • (2) A heartbeat is the event. The individual’s heart contracts at a rate of 1 beat per second (or 60 beats per minute)

Answer 15

More about Hertz

• Frequency is reported with units of hertz (Hz)
• Some people believe that hertz means “cycles per second”
  
  • (1) Hertz means events per second
  • (2) To which event are we referring?
• For example, what is the meaning of a sound wave with a frequency of 100 Hz?
  
  • (1) 100 events occur each second
  • (2) A cycle is our event. In this case, 100 Hz means 100 cycles per second
• What is the meaning of a flat-screen TV with a frame rate of 120 Hz?
  
  • (1) 120 events occur each second
  • (2) A frame is our event. Thus, the TV displays 120 frames per second
• What is the meaning of an individual with a heart rate of 1 Hz?
  
  • (1) One event occurs each second
  • (2) A heartbeat is the event. The individual’s heart contracts at a rate of 1 beat per second (or 60 beats per minute)

Question 16

Three “Bigness” Parameters

• Three parameters describe the size, ____, or ____ of a sound wave:
  
  • (1)
  • (2)
  • (3)

Answer 16

Three “Bigness” Parameters

• Three parameters describe the size, magnitude, or strength of a sound wave:
  
  • (1) Amplitude
  • (2) Power
  • (3) Intensity

Question 17

Amplitude

• Definition— Amplitude is the “____” of a wave
  
  • It is the difference between the ____ value and the ____ or ____ value of an acoustic variable
  • Amplitude is also the difference between minimum value and the ____ value of the ____ variable
• Units— Amplitude can have units of any of the ____ ____
  
  • Amplitude, in relative terms, can also be expressed in ____ (____)
• Typical values— In clinical imaging, pressure amplitude ranges from ____ ____ pascals (____) to ____ ____ pascals (____)
• Determined by— Initially, amplitude is determined only by the ____, the ultrasound system
  
  • However, amplitude decreases as sound propagates through the body
  • The rate at which amplitude decreases as sound propagates depends on the characteristics of both the sound wave and the medium
• Adjustable— ____. A control system on a basic ultrasound system allows the sonographer to ____ initial amplitude of a wave
• Formula—

Answer 17

Amplitude

• Definition— Amplitude is the “bigness” of a wave
  
  • It is the difference between the maximum value and the average or undisturbed value of an acoustic variable
  • Amplitude is also the difference between minimum value and the average value of the acoustic variable
• Units— Amplitude can have units of any of the acoustic variables
  
  • Amplitude, in relative terms, can also be expressed in decibels (dB)
• Typical values— In clinical imaging, pressure amplitude ranges from 1 million pascals (1 MPa) to 3 million pascals (3 MPa)
• Determined by— Initially, amplitude is determined only by the sound source, the ultrasound system
  
  • However, amplitude decreases as sound propagates through the body
  • The rate at which amplitude decreases as sound propagates depends on the characteristics of both the sound wave and the medium
• Adjustable— Yes. A control system on a basic ultrasound system allows the sonographer to alter initial amplitude of a wave
• Formula—

Question 18

What is the difference between amplitude and peak-to-peak amplitude?

• Amplitude is measured from the ____, or undisturbed, value to the ____
• Peak-to-peak amplitude is the ____ between ____ and ____ values of an acoustic variable
  
  • Therefore, peak-to-peak amplitude is ____ the value of the amplitude

Answer 18

What is the difference between amplitude and peak-to-peak amplitude?

• Amplitude is measured from the middle, or undisturbed, value to the maximum
• Peak-to-peak amplitude is the difference between maximum and minimum values of an acoustic variable
  
  • Therefore, peak-to-peak amplitude is twice the value of the amplitude

Question 19

Power

• Definition— Power is the ____ of energy ____ or the ____ at which ____ is performed
  
  • Power, like ____, and ____, describes the “____” of a wave
• Units— Power have the unit of ____
• Typical values— In clinical imaging, typical powers range from ____ to ____ watts (____ to ____ milliwatts), depending on the diagnostic ultrasound technique
• Determined by— Just like amplitude, initial power is determined by the ____, the ultrasound system
  
  • Power ____ as sound propagates through the body
  • The rate at which power ____ as sound propagates depends on the characteristics of the medium and the wave
• Adjustable— ____. Initial power, like amplitude, ____ be changed. A control on the ultrasound systems allows the sonographer to ____ the initial power of a wave
• Formula— ____

Answer 19

Power

• Definition— Power is the rate of energy transfer or the rate at which work is performed
  
  • Power, like amplitude, and intensity, describes the “bigness” of a wave
• Units— Power have the unit of watts
• Typical values— In clinical imaging, typical powers range from 0.004 to 0.090 watts (4 to 90 milliwatts), depending on the diagnostic ultrasound technique
• Determined by— Just like amplitude, initial power is determined by the sound source, the ultrasound system
  
  • Power decreases as sound propagates through the body
  • The rate at which power decreases as sound propagates depends on the characteristics of the medium and the wave
• Adjustable— Yes. Initial power, like amplitude, can be changed. A control on the ultrasound systems allows the sonographer to alter the initial power of a wave
• Formula— Power ∝ Amplitude²

Question 20

How are amplitude and power related?

• Both amplitude and power are parameters that describe ____, or ____, of a wave
• When power increases, ____ ____ amplitude
• Similarly, when power decreases, amplitude ____
• Mathematically, power is ____ to the wave’s amplitude ____, The term is multiplied by itself
• Power ∝ Amplitude²
• [The symbol ∝ means proportional to]

Answer 20

How are amplitude and power related?

• Both amplitude and power are parameters that describe size, or magnitude, of a wave
• When power increases, so does amplitude
• Similarly, when power decreases, amplitude decreases
• Mathematically, power is proportional to the wave’s amplitude squared, The term is multiplied by itself
• Power ∝ Amplitude²
• [The symbol ∝ means proportional to]

Question 21

Intensity

• Definition— Intensity is the ____ of energy in a sound beam
  
  • To calculate intensity, divide the beam’s ____ by the beam’s ____-____ ____
• Intensity, like ____ and ____, describes the “____” of a wave
  
  • Intensity relates to how the power in a wave ____ or is____ in space
  • Therefore, intensity depends on both the ____ in the beam and the ____ over which the power is applied
• Units— The units of intensity are____/____ centimeter, or (____) (watts from ___ and ____ from beam area)
• Typical values— In clinical imaging, intensity ranges from ____ to ____ ____
• Determined by— Just like ____ and____, initial intensity is determined only by the ____, the ultrasound system
  
  • Intensity changes as sound propagates through the body
  • The ____ at which intensity changes as sound propagates depends on the characteristics of both the sound wave and the medium
• Adjustable—____. Initial intensity, like____ and____, ____ be changed
  
  • A control on a basic ultrasound systems allows the sonographer to ____ the initial intensity of a wave
• Formula— ____

Answer 21

Intensity

• Definition— Intensity is the concentration of energy in a sound beam
  
  • To calculate intensity, divide the beam’s power by the beam’s cross-sectional area
  • Intensity, like power and amplitude, describes the “bigness” of a wave
  • Intensity relates to how the power in a wave spreads or is distributed in space
  • Therefore, intensity depends on both the power in the beam and the area over which the power is applied
• Units— The units of intensity are watts/square centimeter, or W/cm² (watts from power and cm² from beam area)
• Typical values— In clinical imaging, intensity ranges from 0.01 to 300 W/cm²
• Determined by— Just like amplitude and power, initial intensity is determined only by the sound source, the ultrasound system
  
  • Intensity changes as sound propagates through the body
  • The rate at which intensity changes as sound propagates depends on the characteristics of both the sound wave and the medium
• Adjustable— Yes. Initial intensity, like power and amplitude, can be changed
  
  • A control on a basic ultrasound systems allows the sonographer to alter the initial intensity of a wave
• Formula— I = P/A

Question 22

More About Intensity

• ____, ____, and intensity are three ____ that describe the ____ or strength of a ____
• These parameters tend to be____ related; Therefore, when intensity____, power and amplitude also____

Answer 22

More About Intensity

• Amplitude, power, and intensity are three parameters that describe the magnitude or strength of a wave
• These parameters tend to be directly related; Therefore, when intensity increases, power and amplitude also increase

Question 23

How is intensity related to power and amplitude?

• When discussing relationships between amplitude, power, and intensity, the word squared always follows the word ____
  
  • Power is related to the amplitude ____
  • Intensity is related to the ____ squared
  • Power is related to the ____

Answer 23

How is intensity related to power and amplitude?

• When discussing relationships between amplitude, power, and intensity, the word squared always follows the word amplitude
  
  • Power is related to the amplitude squared
  • Intensity is related to the amplitude squared
  • Power is related to the intensity

Question 24

Relationship between Intensity and Power

• Mathematically, intensity is ____ to power
• Intensity ∝ Power
• Examples:
  
  • When a wave’s power is____, the intensity is doubled
  • When a wave’s power is quartered, the intensity is ____

Answer 24

Relationship between Intensity and Power

• Mathematically, intensity is proportional to power
• Intensity ∝ Power
• Examples:
  
  • When a wave’s power is doubled, the intensity is doubled
  • When a wave’s power is quartered, the intensity is quartered

Question 25

Relationship between Intensity and Amplitude

• Mathematically, intensity is ____ to the wave’s ____ squared
• The term “squared” means that a number is multiplied by itself
• Intensity ∝ Amplitude²
• Examples:
  
  • When a wave’s amplitude is doubled, the intensity increases to ____ times its original value

Answer 25

Relationship between Intensity and Amplitude

• Mathematically, intensity is proportional to the wave’s amplitude squared
• The term “squared” means that a number is multiplied by itself
• Intensity ∝ Amplitude²
• Examples:
  
  • When a wave’s amplitude is doubled, the intensity increases to four times its original value

Question 26

Wavelength

• Definition— Wavelength is the ____ or ____ of ____ complete cycle
  
  • For example, imagine a sound wave as similar to a train; Wavelength is the length of a single boxcar in a train
• Units— Wavelength is measured in units of mm, meters, or any other unit of ____
• Typical values— In clinical imaging, wavelength in soft tissues ranges from ____ to ____ ____
• Determined by— Wavelength is determined by ____*
  
  • Wavelength is the ____ parameter that is determined by ____
  • Wavelength is speed ____ by frequency
    
    • Speed is determined by the ____ and is ____
    • Frequency is determined by the ____
• Adjustable—____. The wavelength ____ be changed by the sonographer when using a basic ultrasound transducer
• Formula— ____
  
  • λ— ____ or ____
  • c— ____
  • f— ____

Answer 26

Wavelength

• Definition— Wavelength is the distance or length of one complete cycle
  
  • For example, imagine a sound wave as similar to a train; Wavelength is the length of a single boxcar in a train
• Units— Wavelength is measured in units of mm, meters, or any other unit of length
• Typical values— In clinical imaging, wavelength in soft tissues ranges from 0.1 to 0.8 mm
• Determined by— Wavelength is determined by both the source and the medium*
  
  • Wavelength is the only parameter that is determined by both
  • Wavelength is speed divided by frequency
    
    • Speed is determined by the medium and is constant
    • Frequency is determined by the source
• Adjustable— No. The wavelength cannot be changed by the sonographer when using a basic ultrasound transducer
• Formula— λ = c/f
  
  • λ— lamba or wavelength
  • c— speed
  • f— frequency

Question 27

What is the difference between wavelength and period?

• Both wavelength and period describe a ____ cycle in a sound wave
• Wavelength refers to the ____ or ____ of a ____ ____
• Period refers to the ____ that it takes to complete a ____ ____
• Wavelength and period are differentiated by their ____ ; Wavelength has units of ____ , whereas period has units of ____

Answer 27

What is the difference between wavelength and period?

• Both wavelength and period describe a single cycle in a sound wave
• Wavelength refers to the length or distance of a single cycle
• Period refers to the time that it takes to complete a single cycle
• Wavelength and period are differentiated by their units; Wavelength has units of distance, whereas period has units of time

Question 28

What is the relationship between wavelength and frequency?

• As long as a wave remains in one ____, wavelength and frequency are ____ related
• As frequency increases, wavelength ____
• The lower the frequency, the ____ the wavelength

Answer 28

What is the relationship between wavelength and frequency?

• As long as a wave remains in one medium, wavelength and frequency are inversely related
• As frequency increases, wavelength decreases
• The lower the frequency, the longer the wavelength

Question 29

What is the wavelength of 1 MHz sound in soft tissue?

• In soft tissue, sound with a frequency of ____ ____ has a wavelength of ____ ____

Answer 29

What is the wavelength of 1 MHz sound in soft tissue?

• In soft tissue, sound with a frequency of 1 MHz has a wavelength of 1.54 mm

Question 30

What is the rule that defines the relationship between frequency and wavelength of sound in soft tissues?

• To find the wavelength of a sound wave in soft tissue, divide ____ ____ by the frequency in ____:
• wavelength (mm) = (____ ____/____) / ( frequency–____)

Answer 30

What is the rule that defines the relationship between frequency and wavelength of sound in soft tissues?

• To find the wavelength of a sound wave in soft tissue, divide 1.54 mm by the frequency in MHz:
• wavelength (mm) = (1.54 mm/µs) / ( frequency–MHz)

Question 31

Why is wavelength important in diagnostic ultrasound?

• Wavelength plays a very important role in ____ ____
• Shorter wavelengths are created by ____ frequency sound, This usually produces ____ quality images with ____ detail
• Sonographers should try to use ____ frequency transducers rather than ____ frequency transducers

Answer 31

Why is wavelength important in diagnostic ultrasound?

• Wavelength plays a very important role in image quality
• Shorter wavelengths are created by high frequency sound, This usually produces higher quality images with greater detail
• Sonographers should try to use higher frequency transducers rather than lower frequency transducers

Question 32

Propagation Speed

• Definition— Propagation speed is the ____ at which a sound wave travels through a ____
• Units— Speed is measured in units of ____ per ___, ____/µs, or any ____ divided by ____
• Typical values— In the body, the speed of sound ranges from ____ ____/____ to ____ ____/____, depending on the tissue through which it is traveling
• Determined by— Speed is determined only by the ____ through which the sound is traveling
  
  • Speed is not affected by the nature of the sound wave
  • All sound, regardless of the frequency, travels at the same speed through any specific medium
  • This means that sound with a frequency of 5 MHz and sound with a frequency of 3 MHz travel at the ____ propagation speed in the ____ medium
• Adjustable—____. Speed of sound ____ be changed by the sonographer
  
  • Speed ____ ____ when the wave travels from one medium to a different medium
  • Speed is ____ in any given medium
• Formula— speed (m/s) = ____

Answer 32

Propagation Speed

• Definition— Propagation speed is the rate at which a sound wave travels through a medium
• Units— Speed is measured in units of meters per second, mm/µs, or any distance divided by time
• Typical values— In the body, the speed of sound ranges from 500 m/s to 4000 m/s, depending on the tissue through which it is traveling
• Determined by— Speed is determined only by the medium through which the sound is traveling
  
  • Speed is not affected by the nature of the sound wave
  • All sound, regardless of the frequency, travels at the same speed through any specific medium
  • This means that sound with a frequency of 5 MHz and sound with a frequency of 3 MHz travel at the same propagation speed in the same medium
• Adjustable— No. Speed of sound cannot be changed by the sonographer
  
  • Speed changes only when the wave travels from one medium to a different medium
  • Speed is constant in any given medium
• Formula— speed (m/s) = frequency (Hz) x wavelength (m)

Question 33

What is the speed of sound in soft tissue?

• ____ m/s
• ____ mm/µs
• ____ km

Answer 33

What is the speed of sound in soft tissue?

• 1,540 m/s
• 1.54 mm/µs
• 1.54 km

Question 34

What is the speed of sound in biologic tissues other than soft tissue?
- Lung
- Fat
- Soft Tissue (average)
- Liver
- Blood
- Muscle
- Tendon
- Solid bone

Answer 34

What is the speed of sound in biologic tissues other than soft tissue?
- Lung– 500
- Fat– 1,450
- Soft Tissue (average)– 1,540
- Liver– 1,560
- Blood– 1,560
- Muscle– 1,600
- Tendon– 1,700 (1,850)
- Solid bone– 2,000 - 4,800

Question 35

What are the biologic tissues other than soft tissue from slow to fast?

Answer 35

• Lung
• Fat
• Soft Tissue
• Liver
• Blood
• Muscle
• Tendon
• Solid bone

Question 36

What are the biologic tissues other than soft tissue from fast to slow ?

Answer 36

• Solid bone
• Tendon
• Muscle
• Blood
• Liver
• Soft Tissue
• Fat
• Lung

Question 37

What is the speed of sound in other media?

• As a general rule, sound travels fastest in ____, slower in ____, and ____ in gases
• Solids have more particles, it is more ____

Answer 37

What is the speed of sound in other media?

• As a general rule, sound travels fastest in solids, slower in liquids, and slowest in gases
• Solids have more particles, it is more dense

Question 38

What is the speed of sound in air?

Answer 38

SPEED (m/s)
330

Question 39

What is the speed of sound in water?

Answer 39

SPEED (m/s)
1,480

Question 40

What is the speed of sound in metals?

Answer 40

SPEED (m/s)
2,000 - 7,000

Question 41

What characteristics of a medium determine the speed of sound in that medium?

• Two characteristics of a medium affect the speed of sound:
  
  • (1)
  • (2)

Answer 41

What characteristics of a medium determine the speed of sound in that medium?

• Two characteristics of a medium affect the speed of sound:
  
  • (1) Stiffness
  • (2) Density

Question 42

Stiffness

• Stiffness describes the ability of an object to resist ____
• A stiff material will ____ its shape, whereas a non-stiff material will ____ its shape
• How does stiffness affect speed?
  
  • Stiffness and speed are ____ related
  • The speed of sound will be ____ in the ____ medium
• What other terms describe stiffness?
  ____ ____ is the ____ as stiffness
  
  • ____ and ____ are the opposite of stiff
  • A marshmallow may be described as not ____, a ____ bulk modulus, ____ elastic, or highly ____

Answer 42

Stiffness

• Stiffness describes the ability of an object to resist compression
• A stiff material will retain its shape, whereas a non-stiff material will change its shape
• How does stiffness affect speed?
  
  • Stiffness and speed are directly related
  • The speed of sound will be higher in the stiffer medium
• What other terms describe stiffness?
  Bulk modulus is the same as stiffness
  
  • Elasticity and compressibility are the opposite of stiff
  • A marshmallow may be described as not stiff, a low bulk modulus, highly elastic, or highly compressible

Question 43

Density

• Density describes the ____ ____ of a material
• When ____ volumes of two materials are compared, the dense material weighs ____ ____, whereas the non-dense material weighs ____
• How does density affect speed?
  
  • Density and speed are ____ related
  • As materials become more dense (heavier), the speed of sound in the material ____
  • Sound travels faster in media with ____ density
  • If two media are equally stiff, the ____ medium will have a ____ speed

Answer 43

Density

• Density describes the relative weight of a material
• When equal volumes of two materials are compared, the dense material weighs a lot, whereas the non-dense material weighs little
• How does density affect speed?
  
  • Density and speed are inversely related
  • As materials become more dense (heavier), the speed of sound in the material decreases
  • Sound travels faster in media with low density
  • If two media are equally stiff, the denser medium will have a lower speed

Question 44

Period: (Definition)

Answer 44

The time it takes a wave to vibrate a single cycle, or the time from the start of one cycle to the start of the next cycle

Question 45

Period: (Units)

Answer 45

Time, such as microseconds (µs), seconds, hours, or days

Question 46

Period: (Typical values)

Answer 46

0.06 to 0.5 microseconds (µs)

Question 47

Period: (Determined by)

Answer 47

sound source

Question 48

Period: (Adjustable)

Answer 48

No

Question 49

Period: (Formula)

Answer 49

P = 1/f

Question 50

Frequency: (Definition)

Answer 50

The number of cycles that occurs in one second

Question 51

Frequency: (Units)

Answer 51

Units per second, 1/second, hertz, Hz

Question 52

Frequency: (Typical values)

Answer 52

2 MHz to 15 MHz

Question 53

Frequency: (Determined by)

Answer 53

sound source

Question 54

Frequency: (Adjustable)

Answer 54

No

Question 55

Frequency: (Formula)

Answer 55

F = 1/P

Question 56

Amplitude: (Definition)

Answer 56

The difference between the maximum value and the average; The difference between minimum value and the average

Question 57

Amplitude: (Units)

Answer 57

pascals (Pa), kg/cm³, cm, dB

Question 58

Amplitude: (Typical values)

Answer 58

1 million pascals (1 MPa) to 3 million pascals (3 MPa)

Question 59

Amplitude: (Determined by)

Answer 59

sound source

Question 60

Amplitude: (Adjustable)

Answer 60

Yes

Question 61

Amplitude: (Formula)

Question 62

Power: (Definition)

Answer 62

The rate of energy transfer or the rate at which work is performed

Question 63

Power: (Units)

Answer 63

watts

Question 64

Power: (Typical values)

Answer 64

0.004 to 0.090 watts (4 to 90 milliwatts)

Question 65

Power: (Determined by)

Answer 65

sound source

Question 66

Power: (Adjustable)

Answer 66

Yes

Question 67

Power: (Formula)

Answer 67

Power ∝ Amplitude²

Question 68

Intensity: (Definition)

Answer 68

The concentration of energy in a sound beam

Question 69

Intensity: (Units)

Answer 69

watts/square centimeter, or W/cm² (watts from power and cm² from beam area)

Question 70

Intensity: (Typical values)

Answer 70

0.01 to 300 W/cm²

Question 71

Intensity: (Determined by)

Answer 71

sound source

Question 72

Intensity: (Adjustable)

Answer 72

Yes

Question 73

Intensity: (Formula)

Answer 73

I = P/A

Question 74

Wavelength: (Definition)

Answer 74

The distance or length of one complete cycle

Question 75

Wavelength: (Units)

Answer 75

mm, meters, or any other unit of length

Question 76

Wavelength: (Typical values)

Answer 76

0.1 to 0.8 mm

Question 77

Wavelength: (Determined by)

Answer 77

both the source and the medium

Question 78

Wavelength: (Adjustable)

Answer 78

No

Question 79

Wavelength: (Formula)

Answer 79

λ = c/f

Question 80

Propagation speed: (Defintion)

Answer 80

The rate at which a sound wave travels through a medium

Question 81

Propagation speed: (Units)

Answer 81

meters per second, mm/µs, or any distance divided by time

Question 82

Propagation speed: (Typical values)

Answer 82

500 m/s to 4000 m/s

Question 83

Propagation speed: (Determined by)

Answer 83

medium

Question 84

Propagation speed: (Adjustable)

Answer 84

No

Question 85

Propagation speed: (Formula)

Answer 85

speed (m/s) = frequency (Hz) x wavelength (m)

Question 86

Relation Between: Frequency and Period

Answer 86

Inversely

Question 87

Relation Between: Amplitude and Power

Answer 87

Directly

Question 88

Relation Between: Amplitude and Intensity

Answer 88

Directly

Question 89

Relation Between: Power and Intensity

Answer 89

Directly

Question 90

Relation Between: Wavelength and Intensity

Answer 90

Unrelated

Question 91

Relation Between: Wavelength and Frequency

Answer 91

Inversely

Question 92

Relation Between: Acoustic velocity and Density

Answer 92

Inversely

Question 93

Relation Between: Elasticity and Speed of sound

Answer 93

Inversely

Question 94

Relation Between: Acoustic velocity and Compressibility

Answer 94

Inversely

Question 95

Relation Between: Stiffness and sound speed

Answer 95

Directly

Question 96

Relation Between: Frequency and Sound speed

Answer 96

Unrelated

Question 97

Relation Between: Frequency and Intensity

Answer 97

Unrelated

Question 98

Relation Between: Power and Frequency

Answer 98

Unrelated